I've seen similar for dogs and cats but piggies seem to be overlooked. If there was an emergency and for whatever reason I wasn't able to evacuate my pigs (for example, I wasn't in the building at the time) I'd want the emergency services, or public to rescue them if safe to do so. I've also seen little cards people put in their wallets so if they're in an accident, for example by being hit by a car, people can make necessary arrangements to look after their animal(s) whilst they're in hospital.